A ray is defined using undefined terms point and line.
There are three undefined terms from which all other terms in geometry ca be defined; these three terms are; a point, line and a plane.
A point refers to a location in space that has no size, a line is a series of points which extends in two opposite directions without end, while a plane is a flat surface that extends in all directions without end.
A ray is a line with a single endpoint which extends infinitely in on direction. It is defined using the undefined terms point and a line.
